The characteristics of microwave vacuum popping of popcorn and maize according to index of the volume expansion ratio were studied in this paper. With SEM their mechanisms were examined. It was proved that the structure was the important factor which influenced the popping characteristic of popcorn and maize. The fact was found that the popping characteristic of popcorn was better than that of maize, and that the quality of popcorn flower of popcorn and its texture were also better, and that the volume exp...